BackgroundThe invasion of non-native species is a major cause of the global biodiversity loss and creates enormous economic costs. What determines alien invasive species dominance over native plant species is still little known, but there is an emerging pattern that many of the world's worst invasive plants are successful invaders due to the signi cant connection between their clonal traits and invasiveness. Freshwater ecosystems are relatively more prone to decline and extinction of species caused by biological invasion than terrestrial and marine ecosystems. In view of the lack of information about whether or not aquatic alien species at different stages of invasion exhibit any signi cant relation with clonality, the speci c question addressed in this study was whether there is any relationship between clonality and invasiveness in aquatic macrophytes and how does it vary along different stages of invasion? ResultsWhile the link between clonality and species invasiveness has recently been recognized, whether and how clonality varies with different invasion-stages remains open questions. Hence, we tested the relationship between clonality and species invasiveness of Kashmir Himalayan aquatic macrophytes vis-à-vis its variability along different stages of invasion. The data on clonality, stage of invasion, and growth form was obtained through an extensive survey of literature and database like CLO-PLA (CLOnal PLAnts, version 3) and PLADIAS (Plant Diversity Analysis and Synthesis, 2014-2018) followed by evaluation of the clonal organs thorough intensive eld surveys undertaken over a period of 3 years (2014)(2015)(2016)(2017) in different aquatic habitats of the Kashmir valley. Our results showed that 84% of the studied species and almost 90% of the most invasive species (stage V sensu Colautti and MacIsaac 2004) are clonal. A strong positive correlation (r=0.94; p<0.05) between clonality and invasiveness was observed, which further substantiates this association at a broad geographical scale representing the whole region. From the scatter matrix and Pearson's correlation matrix, clonality seems to have a strong positive correlation with fragments, rhizomes, runners, turions, tubers, and buds, thereby further a rming the strong nexus of clonality with species invasions. ConclusionsOur results showed strong association of clonal architecture with not only the stages of invasion but also the distribution pattern of alien species in aquatic habitats, thereby indicating the pivotal contribution of clonality to invasiveness. Future studies directed at unraveling the reasons behind clonality need to be undertaken from the genomic perspective, in order to evolve better models for proper management of alien aquatic invasive species.

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Darwin's naturalization conundrum, which posits that the alien species either succeed in the introduced region because being phylogenetically related to the native species hence being pre-adapted, or are phylogenetically dissimilar to native species and thus occupy unfilled niches, has received a lot of attention but the results have been contradictory. Instead of the usual phylogenetic comparison between native and introduced species to address this conundrum, we followed a novel approach of studying the phylogenetic relationship of a highly widespread and invasive species, Anthemis cotula L. (focal species) separately with the native species and all its co-occurring species (including native and non-native species) along an elevation gradient. The abundance of A. cotula declined continuously with an increase in elevation and species richness. The phylogenetic relationship between the focal species and all the co-occurring species using abundance weighted mean pair-wise distance (MPDaw) showed an increase with an increase in elevation and species richness. A similar but slightly weaker relationship was noticed when the non-abundance weighted mean pair-wise distance (MPDpa) was used. Interestingly, the phylogenetic distance between the focal species and the native species based on MPDaw declined with elevation as well as species richness, but such a decline was seen when MPDpa was used. Our study also revealed that soil nutrients influence the abundance of A. cotula and phylogenetic distance between the focal and other species, thereby indicating the role of micro-ecological factors and spatial heterogeneity in community assembly.

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